The level of hardness in water can have a deleterious effect in many cleaning applications. For example, when hard water alone, or in conjunction with cleaning compositions, contacts a surface, it can cause precipitation of hard water scale on the contacted surface. Scaling is the precipitation of a salt from solution that is supersaturated with respect to the salt. In general, hard water refers to water having a total level of calcium and magnesium ions in excess of about 100 ppm expressed in units of ppm calcium carbonate. Often, the molar ratio of calcium to magnesium in hard water is about 2:1 or about 3:1. The level of water hardness and ratio of calcium to magnesium are influenced by many factors such as geographic location, soil quality, pollutants and pH.
Hard water is also known to reduce the efficacy of conventional alkaline detergents used in the vehicle care, warewashing and laundry industries. One method for counteracting this includes adding chelating agents or sequestrants into detersive compositions that are intended to be mixed with hard water in an amount sufficient to handle the hardness. However, in many instances the water hardness exceeds the chelating capacity of the composition. As a result, free calcium ions may be available to cause precipitation, or to attack active components of the composition causing other deleterious effects, such as poor cleaning effectiveness or lime scale build up.
Alkaline detergents, particularly those intended for institutional and commercial use, generally contain phosphates, nitrilotriacetic acid (NTA) or ethylenediaminetetraacetic acid (EDTA) as a sequestering agent to sequester metal ions associated with hard water such as calcium, magnesium and iron and also to remove soils.
In particular, NTA, EDTA or polyphosphates such as sodium tripolyphosphate and their salts are used in detergents because of their ability to solubilize preexisting inorganic salts and/or soils. When calcium and/or magnesium salts precipitate, the crystals may attach to the surface being cleaned and cause undesirable effects. For example, calcium carbonate precipitation on the surface of ware can negatively impact the aesthetic appearance of the ware, giving an unclean look. The ability of NTA, EDTA and polyphosphates to remove metal ions facilitates the detergency of the solution by preventing hardness precipitation, assisting in soil removal and/or preventing soil redeposition during the wash process.
While effective, phosphates and NTA are subject to government regulations due to environmental and health concerns. Although EDTA is not currently regulated, it is believed that government regulations may be implemented in the future due to environmental persistence. There is therefore a need in the art for an alternative, and preferably environment friendly, cleaning composition that can reduce the content of phosphorous-containing compounds such as phosphates, phosphonates, phosphites, and phosphinates, as well as persistent aminocarboxylates such as NTA and EDTA.
Accordingly it is an object herein to provide an improved process for the prevention of scale in alkaline cleaning such as that used in ware washing, hard surface or CIP cleaning, car washing, instrument cleaning, boiler or cooling tower cleaning, laundry cleaning and the like.
It is another object to provide scale control compositions that may be used in conjunction with a cleaning composition for prevention of scale deposits not only on surfaces to be cleaned, but also on the cleaning machine components themselves.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawings, and the appended claims.